Means for controlling the head pressure in refrigerating systems



1964 R. G. MINER 3,145,543

MEANS FOR CONTROLLING THE HEAD PRESSURE IN TEMS REFRIGERATING SYS 2 Sheets-Sheet 1 Filed Feb. 1, 1960 22 CONDENSER EVAPORATOR K136 INVENTOR ROBERT G. MINER CONDENSER EVAPORATOR ATTORNEYS Aug. 25, 1964 R.- G. MINER 3,145,543

MEANS FOR CONTROLLING THE HEAD PRESSURE IN REFRIGERATING SYSTEMS 2 Sheets-Sheet 2 Filed Feb. 1. 1960 CONDENSER EVAPORATOR FIG. 3

FIG 4 INVENTOR ROBERT G. MINER WV M ATTORNEYS United States Patent 3,145,543 MEANS FOR CGNTROLLING THE HEAD PRES- SURE EN REFREGERATTNG SYSTEMS Robert G. Miner, La Crosse, Wis, assignor to The Trans Company, La Crosse, Wis., a corporation of Wisconsin Filed Feb. l, 1960, Ser. No. 5,900 '7 tllaims. ((11. 62-149) This invention relates to means for controlling the head pressure in refrigerating systems and has for an object to regulate the level of the refrigerant liquid in the condenser to vary the magnitude of the effective heat transfer surface inside the condenser. Head pressure is defined as the pressure existing in the system between the compressor and the expansion device.

Another object of the invention is to provide means for heating the refrigerant in the receiver of the refrigerating system and to provide means for reducing the flow of refrigerant liquid through the receiver to vaporize a portion of the refrigerant liquid in the receiver and thus reduce the amount of refrigerant liquid in the receiver when the head pressure tends to fall below a predetermined minimum.

Another object of the invention is to provide means for supplying discharge gas to the receiver for the purpose of heating the receiver.

Another object of the invention is to provide means for regulating the flow of liquid refrigerant through the receiver of a refrigeration system in response to the head pressure.

Another object of the invention is to provide means for supplying heat to the receiver of a refrigeration system and means for varying the amount of heat supplied in response to the head pressure in order to vary the amount of liquid refrigerant in the receiver.

Other objects and advantages of the invention will become apparent as the specification proceeds to describe the invention with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a first form of the invention;

FIG. 2 is a diagrammatic view of a second form of the invention;

FIG. 3 is a diagrammatic view of a third form of the invention; and

FIG. 4 is an enlarged cross-sectional view to show the restrictor and the liquid line to the receiver of the form of FIG. 3.

In a refrigerating system, the head pressure is related to the condensing temperature of the refrigerant in the condenser which in turn is governed by the temperature of the fluid removing heat from the condenser and the refrigerant therein. For instance, in the case of an air cooled condenser, any substantial drop in ambient air temperature can result in a decrease of head or high side pressure to such an extent that the rate of flow through the expansion valve or other expansion means is substantially reduced thereby reducing the refrigerating capacity. Reduction in the heat absorbed by the evaporator will also lessen the head or high side pressure. This invention eliminates such disadvantages by automatically maintaining a satisfactory head pressure regardless of the temperature of the condenser coolant, and the rate of heat absorption by the evaporator.

It should be pointed out here that the interior surface of the condenser which is contacted by refrigerant gas is much more eifective in heat transfer than the interior surface of the condenser which is contacted by liquid. It is, therefore, evident that partial flooding of the condenser causes a corresponding partial reduction of its heat transfer with a corresponding increase in the head or high side pressure of the system. Control of the liquid level in the condenser maintains a predetermined head or high side pressure regardless of the temperature of the condenser coolant or the rate of heat absorption by the evaporator.

Referring to the form of the invention illustrated in FIG. 1, a compressor 10 compresses refrigerant gas from the evaporator 12, and the compressed gas flows to condenser 14 through conduit 16. These components may be of any well known construction. The evaporator 12 is assumed to be cooling air or other gas and has the usual fan 18 driven by a motor (not shown). The condenser may be cooled by various fluids but it is assumed to be cooled by air or other gas and has the usual fan 20 driven by a motor (not shown). The liquid condensed in the condenser 14 flows through a conduit 22. During normal operation when the head pressure does not tend to drop below the desired value, liquid refrigerant flows from the conduit 22 through conduit 24 to valve 26 and thence through conduit 28 to the receiver 30. From the receiver 3i), the liquid refrigerant flows through conduit 32 to conduit 34, and thence through the expansion valve 36 to the evaporator 12. The expansion valve 36 has the usual thermostatic bulb 33 responsive to the temperature of the refrigerant gas leaving the evaporator 12. Also during normal operation, a portion of the refrigerant liquid flowing in conduit 22 flows through a restrictor 40 to conduit 34.

A portion of the gas flowing in conduit 16 flows through a parallel conduit 42 containing a heating coil 44 normally submerged in the liquid of the receiver 30. During normal operation, the cool liquid refrigerant from conduit 28 is flowing through the receiver 30 and the effect of heater 44 is negligible.

The valve 26 will now be described. The head pressure acts upon a diaphragm 46 and is opposed by a spring 48, the tension of which may be adjusted by screw 50 so that when the head pressure tends to be normal, the valve plug 52 is spaced from the port 54 to allow substantially unobstructed flow through the port 54. A hole 50 in the valve 26 provides for atmospheric pressure on the spring side of the diaphragm 46.

The operation of the form of FIG. 1 will now be described. When the conditions such as temperature of condenser coolant or evaporator load are such that the head pressure does not tend to fall below the desired value called normal, the valve 26 is open, and the liquid refrigerant is flowing through the receiver 30 from conduit 28 to eliminate the effect of the heater 44. As the head pressure tends to fall below the desired predetermined minimum, the valve 26 closes the desired amount 30 to reduce the flow of liquid refrigerant through the receiver from conduit 28 and the heat from the heater 44 vaporizes refrigerant in the receiver to drive out some of the liquid. The liquid driven out of the receiver 30 causes liquid to back up in the condenser 14 because the condenser 14 is the only space in the system which can receive the additional liquid. When the liquid level rises in the condenser 14, its capacity is reduced and the condensing pressure or head pressure is prevented from falling below the desired predetermined minimum.

Referring now to FIG. 2 in which parts corresponding to parts in FIG. 1 have like numerals, a three way valve 56 controls the flow from conduit 22 to conduit 28 and conduit 34. Valve 56 has a port 58 communicating with conduit 28 and a port 60 communicating with con duit 34. A valve plug 62 is secured to diaphragm 64 and is movable thereby to a position to close either of the ports 53 or 60 or to some intermediate position. Head pressure acts upon the diaphragm 64 and is opposed by spring 66, the tension of which may be adjusted by screw 68 so that when the head pressure tends to be normal, the valve plug 62 closes or substantially closes port 6t and allows substantially unobstructed flow 3 through port 58. A hole 70 in the valve 56 provides for atmospheric pressure on the spring side of the diaphragm 64.

The operation of the form of FIG. 2 will now be described. During normal operation of the system when the head pressure does not tend to fall below the desired predetermined minimum, the valve plug 62 is positioned to permit substantially unobstructed flow through port 58 into conduit 28. The cooled liquid 28 flowing through receiver 30 substantially eliminates the heating effect of the heater 44. When the head pressure tends to fall below the desired predetermined minimum, the valve plug moves toward port 58 and away from port 60 thus directing more of the liquid into conduit 34- and less through conduit 28. As less cooled liquid flows through receiver 30 from conduit 28, heat from heater 44 vaporizes refrigerant and the liquid refrigerant in the receiver 30 is forced out and causes liquid refrigerant to back up in the condenser with the same effect as in the form of FIG. 1 described above.

The form of the invention of FIG. 3 will now be described. Parts which correspond to parts in FIGS. 1 and 2 have like numerals. As in the first two forms of the invention, a portion of the gas flowing in conduit 16 may be allowed to flow through a parallel conduit 42 containing a heating coil 44 normally submerged in the liquid of the receiver. In the form of the invention of FIG. 3, this conduit has a valve 72 which is closed or substantially closed when the head pressure is normal or in other words above the desired predetermined minimum. The head pressure acts upon a diaphragm 74 and is opposed by a spring 76, the tension of which may be adjusted by a screw 78 so that when the head pressure tends to be normal, the valve plug 8% is in closing position with respect to a port 82. A hole 83 in the valve 72 provides atmospheric pressure on the spring side of the diaphragm '74. When the port 82 is closed there is no flow through the heater 44. However, when the head pressure tends to fall below the desired predetermined minimum, the valve 72 uncovers port 82 and refrigerant flows from conduit 16 through heater 44 and thence through the valve 72 back to the conduit 16. As shown in FIG. 4, the restrictor 41 is larger than restrictor 40 of FIG. 1 so that only a small portion of the liquid flowing through conduit 22 passes through small conduit 25 to the receiver 30.

It is thus seen that during normal operation there is no flow through heater 44 and a small flow of liquid refrigerant from conduit 25 to the receiver 30 is suflicient to maintain the receiver 30 at substantially condensing temperature. Under these conditions a considerable amount of liquid refrigerant is maintained in the receiver 30 as shown in the drawing. However, when the head pressure tends to fall below the desired predetermined minimum, the valve 72 opens to allow hot refrigerant gas to flow to the heater 44 and vaporize a portion of the liquid in the receiver 30 and drive some of the liquid from the receiver 30 into the system to back up liquid in the condenser 14 to reduce its effectiveness and maintain the desired predetermined minimum head pressure.

Although I have described specific embodiments of my invention, I contemplate that various modifications may be made without departing from the scope or spirit of my invention and I desire to be limited only by the claims.

I claim:

1. In a refrigeration system comprising interconnected compressor, condenser, evaporator, receiver, and an expansion device in operative relationship to the inlet to theevaporator, means for preventing the head pressure in the system upstream of the expansion device from falling below a predetermined minimum regardless of of the temperature of the condenser coolant or rate of heat absorption by the evaporator, by controlling the level of liquid refrigerant in the condenser, said means comprising means for vaporizing liquid refrigerant in the receiver to force liquid refrigerant from the receiver to the condenser and means for controlling said last mentioned means responsive to head pressure.

2. In a refrigeration system comprising interconnected compressor, condenser, evaporator, receiver, and an expansion device in operative relationship to the inlet to the evaporator, means for preventing the head pressure in the system upstream of the expansion device from falling below a predetermined minumum regardless of the temperature of the condenser coolant or rate of heat absorption by the evaporator, by controlling the level of liquid refrigerant in the condenser, said means comprising means for heating liquid refrigerant in the re ceiver, means for supplying cooled refrigerant liquid to the receiver and means for controlling one of said last two mentioned means responsive to head pressure to vaporize refrigerant liquid in said receiver and force liquid refrigerant from the receiver to the condenser when the head pressure falls below a predetermined minimum.

3. In a refrigeration system comprising, a compressor, a condenser, a first conduit for conducting refrigerant gas from said compressor to said condenser, an evaporator, a second conduit for conducting refrigerant from said condenser to said evaporator, an expansion device in said second conduit adjacent the inlet of said evaporator, a third conduit for conducting refrigerant from said evaporator to said compressor, a receiver, a fourth conduit for conducting refrigerant from said condenser to said receiver, a fifth conduit for conducting refrigerant from said receiver 'to said expansion device, a sixth conduit connected in parallel with said first conduit, said sixth conduit conducting refrigerant and being in heat transfer relationship with the refrigerant in said receiver, means for throttling the flow in said fourth conduit, and means responsive to head pressure for controlling said throttling means 4. A refrigeration system comprising, a compressor, a condenser, a first conduit for conducting refrigerant gas from said compressor to said condenser, an evaporator, a second conduit for conducting refrigerant from said condenser to said evaporator, an expansion device in said second conduit adjacent the inlet of said evaporator, a third conduit for conducting refrigerant from said evaporator to said compressor, a receiver, a fourth conduit for conducting refrigerant from said condenser to said receiver, a fifth conduit for conducting refrigerant from said receiver to said expansion device, a sixth conduit connected in parallel with said first conduit, said sixth conduit conducting refrigerant and being in heat transfer relationship with the refrigerant in said receiver, a three way valve connected to receive refrigerant from said condenser and to discharge said refrigerant into said second conduit and said fourth conduit and means responsive to head pressure for controlling said three way valve to proportion the flow of refrigerant between said second and fourth conduits to maintain a predetermined minimum head pressure.

5. In a refrigeration system comprising, a compressor, a condenser, a first conduit for conducting refrigerant gas from said compressor to said condenser, an evaporator, a second conduit for conducting refrigerant from said condenser to said evaporator, an expansion device in said second conduit adjacent the inlet of said evaporator, 21 third conduit for conducting refrigerant from said evaporator to said compressor, a receiver, a fourth conduit for conducting refrigerant from said condenser to said receiver, a fifth conduit for conducting refrigerant from said receiver to said expansion device, a sixth conduit connected in parallel with said first conduit, said sixth conduit conducting refrigerant and being in heat transfer relationship with the refrigerant in said receiver, means for throttling the flow in said sixth conduit, and means responsive to the head pressure for controlling said throttling means to increase the flow when the head pressure falls below a predetermined minimum.

6. In a refrigeration system comprising, a compressor, a condenser, a first conduit for conducting refrigerant gas from said compressor to said condenser, an evaporator, a second conduit for conducting refrigerant from said condenser to said evaporator, an expansion device in said second conduit adjacent the inlet of said evapo rator, a third conduit for conducting refrigerant from said evaporator to said compressor, a receiver, a fourth conduit for conducting refrigerant from said condenser to said receiver, a fifth conduit for conducting refrigerant from said receiver to said second conduit adjacent said expansion device, a sixth conduit connected in parallel with said first conduit, said sbrth conduit conducting refrigerant and being in heat transfer relationship with the refrigerant in said receiver, a restrictor in said second conduit downstream from said fourth conduit and upstream from the junction of said second and fifth conduit, means for throttling the flow in said fourth conduit, and means responsive to head pressure for controlling said throttling means to reduce the flow when the head pressure falls below a predetermined minimum.

'7. A refrigeration system comprising, a compressor, a condenser, a receiver connected with the condenser to receive refrigerant therefrom, an evaporator, a conduit connecting the receiver with the evaporator for supplying refrigerant to the evaporator, a conduit connecting the evaporator with the compressor for conducting refrigerant to the compressor, a conduit connecting the discharge of the compressor With the condenser, conduit for supplying hot uncondensed refrigerant in heat transfer relationship to the receiver to vaporize liquid refrigerant in the receiver and force liquid refrigerant from the receiver to the condenser to vary the effectiveness of the condenser, a valve in said last mentioned conduit and means responsive to head pressure proportionately controlling said valve.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A REFRIGERATION SYSTEM COMPRISING INTERCONNECTED COMPRESSOR, CONDENSER, EVAPORATOR, RECEIVER, AND EXPANSION DEVICE IN OPERATIVE RELATIONSHIP TO THE INLET TO THE EVAPORATOR, MEANS FOR PREVENTING THE HEAD PRESSURE IN THE SYSTEM UPSTREAM OF THE EXPANSION DEVICE FROM FALLING BELOW A PREDETERMINED MINIMUM REGARDLESS OF OF THE TEMPERATURE OF THE CONDENSER COOLANT OR RATE OF HEAT ABSORPTION BY THE EVAPORATOR, BY CONTROLLING THE LEVEL OF LIQUID REFRIGERANT IN THE CONDENSER, SAID MEANS COMPRISING MEANS FOR VAPORIZING LIQUID REFRIGERANT IN THE RECEIVER TO FORCE LIQUID REFRIGERANT FROM THE RECEIVER TO THE CONDENSER AND MEANS FOR CONTROLLING SAID LAST MENTIONED MEANS RESPONSIVE TO HEAD PRESSURE. 